Earlier experiments have shown that the RNA from many bacterial species, including Escherichia coli and Bacillus subtilis, is extensively polyadenylated. That poly(A) sequences are associated with specific bacterial RNA molecules has been clearly confirmed by the cloning and sequencing of DNA complementary to bacterial poly(A)-RNA and the demonstration of poly(A) sequences at the 3'-termini of the transcripts derived from the 1pp, trpA, ompA, and phoA genes of E. coli. The proposed experiments aim to define the nucleotide sequences at which polyadenylation of specific bacterial mRNA molecules occurs, to study the structural requirements of mRNA polyadenylation by site-directed mutagenesis and deletion mutation, and to define the mechanism of polyadenylation and its relationship to transcription termination by in vitro experiments. The physiological function of mRNA polyadenylation in E. coli and B subtilis will be explored by studying the effect of polyadenylation on mRNA stability and its response to various physiological and genetic factors, using specific mRNAs as experimental models.